In recent years, image display devices (PLD: Paper-Like Display) which are thin like paper, convenient to carry, and capable of displaying letters and images have attracted attention. Since such image display devices have visibility and portability, that are advantages of paper as normal printed matter, and are electrically rewritable information, there have been attempts to put the image display devices into practical use as an alternative to paper in view of environment aspect and cost aspect.
Various types such as a type for moving particles by electrophoresis or the like, a liquid crystal type, and an electrochemical type are devised as display techniques of image display devices (for example, see Non-Patent Literature 1).
Particularly, a microcapsule electrophoresis type, a microcup electrophoresis type, an electronic liquid powder type, a toner display type, and the like are considered as the type for moving particles. In the cases of these types, black and white particles, which are display mediums, are enclosed between transparent electrodes and an electric field is applied to electrically move the particles, thereby forming and displaying monochrome images. Active driving and passive driving are employed as a method for driving an image display device, and a back surface technique (panel circuit) for an image display device is also considered.
In the case of the image display device of the above-described particle movement type, a partition wall is required to enclose black and white particles as described above. As a method for forming such a partition wall, a mold transfer method, a screen printing method, a sandblast method, a photolithography method, and an additive method or the like is proposed (for example, see Patent Literature 1). Among them, a photolithography method which uses a photosensitive resin composition to efficiently form a high-definition pattern upon irradiation with active light rays is attracting attention.
In recent years, an example in which a full-color display is realized by combining a color filter with the monochrome image display has also been reported (for example, see Non Patent Literature 2).
In addition, despite differing from the above-described PLD, a display (laser drawing-type display) which displays an image by drawing and excitation of a fluorescent material with a semiconductor laser has attracted attention in recent years. Since this display has a simple structure, the manufacturing cost thereof is low, and since only a display pixel is drawn by the laser, the display has a characteristic in that it is excellent in terms of low power consumption. It is required for this display to have a partition wall since it is required to partition and enclose the fluorescent material. As a method for forming such a partition wall, there are various methods as in the case of the PLD, and among them, a photolithography method capable of efficiently forming a high-definition pattern is attracting attention.
A partition wall of an image display device using the photolithography method is formed as follows. That is, the partition wall of the image display device is formed through a method including the steps of: laminating a light-shielding layer, called a black matrix, on a substrate by a photolithography technique depending on the case; applying a photosensitive resin composition or laminating a photosensitive film (photosensitive element) on the light-shielding layer to form a photosensitive resin composition layer; irradiating a predetermined portion of the photosensitive resin composition layer with active light rays to photocure the exposed portion; and removing the unexposed portion to form a photocured pattern. Accordingly, it is generally required for a photosensitive resin composition for forming a partition wall of an image display device to have patterning properties (sensitivity, resolution, and adhesion to a substrate).
When an image display device for a PLD is manufactured, a step of filling the photocured pattern obtained in the above-described step with a display medium such as particles, a step of heat-treating the photocured pattern, a step of attaching an electrode substrate, and the like are further included. Accordingly, an image display device having a cured photosensitive resin composition layer as a partition wall is obtained. Since a high-temperature process is essential in the above-described steps, the partition wall of the image display device which is formed using the photosensitive resin composition is required to have heat resistance and the like.
In addition, when a laser drawing-type display is manufactured, a step of heat-treating the photocured pattern obtained in the above-described step or a step of coating the inside of the photocured pattern with a fluorescent material or the like is further included. Accordingly, a laser drawing-type display having a cured photosensitive resin composition layer as a partition wall is obtained.
Furthermore, a partition wall material is desired to have gray to black colors depending on the display or intended use. The reason for this is that when the partition wall has the above-described colors, it is possible to expect an effect in which sharp colors are shown upon display of images.
The following Patent Literatures 2 to 4 disclose a photosensitive resin composition for forming a partition wall of an image display device.